The objectives of this study are to conduct (1) a randomized therapeutic trial to determine whether argon laser photocoagulation has a beneficial effect on hemorrhagic retinopathies associated with both central retinal vein occlusion and major branch vein occlusion, and (2) prospective natural history studies on various types of retinal vein occlusion, i.e., venous stasis retinopathy, hemorrhagic retinopathy, hemi-central retinal vein occlusion, major retinal branch vein occlusion and macular venular occlusion. The patients will be followed serially at periodic intervals by meticulous testing of the visual functions (i.e., visual acuity and visual fields) and ocular evaluation (particularly retinal changes).